adapt makefile to conform to CTAN preferences

according to Robin Fairbairns:

>    btw, the least error-prone format for the zip file is:
>
>      xyz.zip ->
>        xyz.tds.zip (if available)
>        xyz/
>          [actual distribution of package xyz]
sync with Context as of date
sync with Context as of 2013-08-12
sync with Context as of 2013-08-24
Merge pull request #16 from phi-gamma/master

routine update to latest code